Assistant Commissioner Malcolm Burgess told TV3's Campbell Live tonight that police had been investigating a new allegation against Frandi.
There was an agreement between the police informant and investigating officers to keep the detail of the new allegation "under wraps until an appropriate time'', Mr Burgess said.
"Unfortunately Mr Frandi became aware of it on Saturday ...''
An off-duty officer in Timaru was contacted on Saturday by someone who knew Frandi and was concerned by what he may do.
The officer quickly made contact with Waimate police, who spoke with the person who knew Frandi.
"We went to find Mr Frandi and he had left his address and he never returned,'' Mr Burgess said.
"As soon as they (Waimate police) knew that these concerns existed they acted and I'm confident that they acted promptly and effectively.''
When asked about reports that in 2000 Frandi spoke about taking a girl into the forest and committing crimes against her, Mr Burgess said: "It's a pretty chilling scenario.''
Mr Burgess said he was confident the homicide inquiry would cover the police reaction to the information received on Saturday.
He said if those details needed to be more closely examined there could be an internal inquiry.
Dagmar Pytlickova had been in New Zealand since January and was working at a Cromwell vineyard.
"Dasha's family in the Czech Republic have been informed and say they are shocked and devastated about what has happened. They are still coming to terms with the news and have requested privacy,'' Mr Williams said.
"I guess the thing we can do now is try and make as much sense of it as we can for Dasha's family ...''
Mr Williams confirmed that Frandi was known to police and was given a three-and-a-half year prison sentence in 2000 for abduction of a 19-year-old woman for sex.
"What I would say is that what has occurred in this situation seems very similar to what occurred in 2000.''
As well as the kidnapping conviction, Frandi was also convicted and fined for common assault in 2005, and for cultivating cannabis and minor traffic offending in 2006.
Mr Williams said Frandi was also under investigation for allegations of child molestation after police received several complaints and that will be another aspect of the inquiry.
Today police also found Frandi's silver BMW car in trees about 3km from where the bodies were found.
A close friend of Frandi, who agreed to be interviewed on condition his name was not used, said the Waimate local came from a troubled background.
"He had a number of issues, he didn't talk too much about his family other than that there were problems there. He kept things to himself.
"He was a loner, basically. Somebody else has said exactly the same thing, and he was.''
His father, Arthur Frandi, a barman at the local town and country club, died of cancer a few years ago.
"Jason took it reasonably hard but I don't think that's the only problem. He comes from a troubled background.''
The friend said he had tried to nurture Frandi when he was a troubled teenager.
"I did take him under my wing to some extent when he was younger and I felt he sort of came right when he had a good job.
"I feel a bit sad that I didn't pick up something when I saw him last week.''
